Relevance to NIAID Mission: A mentored award to allow this young investigator to develop his analytical and technical research skills, with a career goal of independently directing research into parasite biology, pathogenesis, and therapy. [unreadable] [unreadable] Background: New medications are urgently needed for the prevention and treatment of falciparum malaria. The efficient and timely development of such drugs depends upon a fuller understanding of Plasmodium's biology, particularly the molecular pathways critical for its survival. One such pathway may involve phosphodiesterases (PDEs), which are essential for the normal, growth, and differentiation of other protozoan parasites, but which remain poorly characterized in the Plasmodium species that cause malaria. [unreadable] [unreadable] Primary Hypothesis: The normal growth and differentiation of Plasmodium falciparum depends upon the expression and activity of its phosphodiesterases. [unreadable] [unreadable] Research Design and Methods: To study the biochemical and structural characteristics of the PDEs, we will heterologously express their recombinant catalytic domains, and determine the activity of the native PDEs from lysates of P. falciparum cultures. We will determine the mRNA and protein expression levels of all four PDEs with quantitative PCR of each PDE on mRNA harvested from different life cycle stages, and with Western blotting of protein lysates from different life-cycle stages with antibodies mono-specific for each PDE. We will learn whether P. falciparum's PDEs are located in specific intracellular locations by performing immunqlocalization with confocal laser scanning microscopy. Finally, we will discover the effects of perturbing PDE function within the parasite by disrupting each PDE gene and observing phenotypic alterations, and by probing the biological functions of the PDEs with a "toolkit" of small molecules that inhibit each PDE specifically. [unreadable] [unreadable] Relevance to Public Health: These experiments will answer fundamental questions about the role of phosphodiesterases (which are signaling molecules) in P. falciparum's biology and its ability to cause malaria. To date, this area remains little explored, but it promises to provide important insights into the pathogenesis and treatment of this deadly illness. [unreadable] [unreadable]